At least two congressional Democrats have put up calls for Trump to be impeached over claims that the President disclosed classified secrets to Russian foreign minister about a planned Islamic State operation during their meeting last week.

House Democrats Al Green and Maxine Waters have urged Congress to impeach Trump in the wake of the latest bombshell allegations, coming on the heels of the shock firing of FBI director James Comey last week. The lawmakers say Trump’s dismissal of Comey — who was overseeing probes into possible Trump campaign collusion with Russia to skew the 2016 election — amounts to an attempt to hinder the counterintelligence investigations.

A number of media personalities urged the president to resign following the claim that he divulged highly classified information about the Islamic State group to the Russian foreign minister, Sergei Lavrov, and its ambassador to Moscow Sergey Kislyak. “The president should resign,” wrote David Frum, a conservative editorial writer for the Atlantic, a call echoed by influential TV satirist Stephen Colbert who urged the US leader: “Donald Trump, if you’re watching, first of all: You’re a bad president. Please resign.”

Constitutional law expert Laurence Tribe argued even before the latest explosive reports that sufficient evidence had accrued since Trump took office in January to merit launching an impeachment investigation.

“The country is faced with a president whose conduct strongly suggests that he poses a danger to our system of government,” he wrote in the Washington Post at the weekend. The US impeachment process — a Constitutional method for removing the president or other federal officials from office on the grounds of “treason, bribery, and other high crimes and misdemeanors” — involves several stages.

If a majority of the House votes in favor of impeachment, the Senate will then hold a trial. To convict and oust the president the Senate must achieve the high threshold of a two-thirds vote. No influential lawmaker has thus far spoken out in support of impeaching Trump. However, Reuters, quoting two U.S. officials with knowledge of the meeting said the intelligence Trump shared with Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergei Kislyak, was supplied by a U.S. ally in the fight against the militant group. The White House said the allegations, first reported by the Washington Post, were not true.

“The story that came out tonight as reported is false,” H.R. McMaster, Trump’s national security adviser, told reporters at the White House, adding that the two men reviewed a range of common threats including to civil aviation.

“At no time were intelligence sources or methods discussed. The president did not disclose any military operations that were not already publicly known. … I was in the room. It didn’t happen,” he said. The White House also released a statement from Secretary of State Rex Tillerson, who said the meeting focused on counterterrorism, and from deputy national security adviser Dina Powell, who said the Post story was false. Reacting to the news, the Senate’s No. 2 Democrat, Dick Durbin, called Trump’s conduct “dangerous” and reckless.” The Republican head of the Senate Foreign Relations Committee, Bob Corker, called the allegations “very, very troubling” if true. One of the officials said the intelligence was classified Top Secret and also held in a secure “compartment” to which only a handful of intelligence officials have access.

After Trump disclosed the information, which one of the officials described as spontaneous, officials immediately called the CIA and the National Security Agency, both of which have agreements with a number of allied intelligence services, and informed them what had happened. While the president has the authority to disclose even the most highly classified information at will, in this case he did so without consulting the ally that provided it, which threatens to jeopardize what they called a longstanding intelligence-sharing agreement, the U.S. officials said.

‘NO FILTER’

In his conversations with the Russian officials, Trump appeared to be boasting about his knowledge of the looming threats, telling them he was briefed on “great intel every day,” an official with knowledge of the exchange said, according to the Post. U.S. officials have told Reuters they have long been concerned about disclosing highly classified intelligence to Trump. One official, who requested anonymity to discuss dealing with the president, said last month: “He has no filter; it’s in one ear and out the mouth.”